firmware: ti_sci: Use struct ti_sci_resource_desc in get_range ops

Use the ti_sci_resource_desc directly and update it's start and num members
directly instead of requiring individual parameters for them.

This will allow easy extension of the RM parameters without changing API.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>